Please check the solution I have added.

For a a fixed n the number of trees is \( n^2\) and the number of trees NOT on he edge is \((n-2)^2=n^2-4n+4\).

So the number of trees on the edge is

\(K=n^2-n^2-4n+4=4n-4=4(n-1)
\)

which is clearly divisible by 4

The total number of trees around the edge (k) will always be a multiple of 4
Here's why:

Notice that we can take this arrangement of trees...


... and divide the trees into 4 groups of 3, and 4 groups of 1

So, the total number of trees in this example = (4)(3) + (4)(1) = 4(3 + 1) = 4(4)
This means the total number of trees is a multiple of 4


Similarly, we can take this arrangement of trees...


... and divide the trees into 4 groups of 5, and 4 groups of 1

So, the total number of trees in this example = (4)(5) + (4)(1) = 4(5 + 1) = 4(6)
This means the total number of trees is a multiple of 4

As you can see, we can use this approach to show that the total number of trees will always be a multiple of 4

When we check the answer choices, only one answer choice (276) is a multiple of 4

So, the correct answer is E

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